The conventional unrecoverable line-type temperature sensitive detector is a widely used fire detector. FIG. 1 and FIG. 2 illustrate the conventional unrecoverable line-type temperature sensitive detector and the cross sectional view of its detecting cable. The detecting cable of the detector comprises a sheath 1 having two or more than two (eg. 3 or 4 etc.) detecting conductors 3 twisted with each other therein. The detecting conductor may be elastic conductor, such as shape-memory alloy wire. The detecting conductors are wrapped with a plastic layer 2 with a certain melting point. While the detecting cable is heated, the plastic layer is softened or melted, and the conductors then contact each other under the elastic force of the elastic conductors (or the shape memory alloy wires). Thus, short circuit occurs, thereby performing fire alarm. The advantages of the detector are as follows. That is, the detecting cable may conduct short-circuit alarm when the temperature of any point of the detecting cable reaches a prescribed temperature for alarming. The sensitivity of the detector is irrelevant to the length being heated. Accordingly, the detector is highly sensitive when an article to be protected is overheated in part or the fire is caused from outside. Also, when one conductor of the detector is disconnected, the fault alarm would take place anyway. The disadvantages lie in that the temperature sensitive detector does not have fault alarm function for short circuit, and there is only fire alarm function for short circuit. Therefore, it is hard to distinguish the short-circuit fault from the short-circuit fire alarm signal. Accordingly, an unrecoverable line-type temperature sensitive detector having short-circuit fault alarm function that is capable of distinguishing short-circuit fault from short-circuit caused by fire is desired.